Stress on human body tends to increase with the complication of social environment, and thus an increased number of patients complain of symptoms such as sleep duration disorder, insomnia and the like, which are considered to be induced by stress.
Although the physiological phenomenon named sleep is very complicated and its mechanism has not been elucidated in detail, several nucleic acid-related compounds which affect sleep have been reported. Such compounds include the following:
(1) Uridine
Sleep-promoting effect [see Biomed. Res., 4, 223 (1983); Neurosci. Res., 1, 243 (1984); Proc. Natl. Acad. Sci. U.S.A., 81, 6240 (1984); Neuroscience Letters, 49, 207 (1984)];
(2) Uracil
Hexobarbital induced sleep potentiating effect [see J. Am. Pharm. Assoc., 44, 56 (1955); ibid., 44, 550 (1955)];
(3) N.sup.3 -Benzyluridine and its derivatives
Hypnotic effect and/or pentobarbital induced sleep potentiating effect [see Chem. Pharm. Bull., 33, 4088 (1985); Japanese Patent Laid-Open Publication No. 207218/1987];
(4) N-Allyl or N-benzyl substituted derivatives of uracil, thymine or 6-methyluracil
Hypnotic effect and/or pentobarbital induced sleep potentiating effect [see Chem. Pharm. Bull., 35, 4982 (1987); Abstract of the Proceedings of the 108th Annual Meeting of Pharmaceutical Society of Japan, page 708 (1988)].
It has been also reported that the N-allyl substituted derivative of uracil (N.sup.1,N.sup.3 -diallyl uracil) and uridine have anticonvulsive effect [see Brain Res., 55, 291 (1973); Chem. Pharm. Bull., 35, 4928 (1987)].
However, these conventional compounds (i) have no hypnotic effect though they exhibit sleep-promoting effect (uridine and uracil), and (ii) must be administered in large doses (320-752 mg/kg) to induce sleep by intraperitoneal injection, and thus they do not always have satisfactory effects.
An object of the present invention is to provide a central nervous system depressant which comprises as an active ingredient a compound exhibiting more potent central nervous system depressant effects such as hypnotic effect, sleep-promoting effect, anticonvulsive effect and the like than the conventional compounds.